0

Guest

Courses New

An object moving at speed 40cm/sec towards a concave mirror of focal kenght 20cm.When the object is at distance 60cm,the speed of image is

An object moving at speed 40cm/sec towards a concave mirror of focal kenght 20cm.When the object is at distance 60cm,the speed of image is
 

Grade:12th pass

1 Answers

Piyush Kumar Behera
417 Points
5 years ago
\frac{1}{f}=\frac{1}{u}+\frac{1}{v}
Differentiating the expression w.r.t. time
0=\frac{1}{v^{2}}\frac{du}{dt}+\frac{1}{u^{2}}\frac{dv}{dt}
\frac{dv}{dt}=-\frac{v^{2}}{u^{2}}\frac{du}{dt}
 
Just find the final position of the image by using the mirror formula...
\frac{1}{-20}=\frac{1}{-60}+\frac{1}{v}
 
Solving we get
v = – 30 cm
 
Now using this formula we get
\frac{dv}{dt}=-\frac{v^{2}}{u^{2}}\frac{du}{dt}
\frac{dv}{dt}=-\frac{(-30)^{2}}{(-60)^{2}} *40
 
\frac{dv}{dt}=-\frac{1}{4}*40
\frac{dv}{dt}=-10 cm/sec
 
So the velocity of the image is 10 cm/sec opposite to the direction of the velocity of object.
 
Piyush Kumar Behera
IIT Dhanbad
 
 

Think You Can Provide A Better Answer ?

Other Related Questions on Modern Physics

View all Questions »

ASK QUESTION

Get your questions answered by the expert for free

Answer and earn gift vouchers

Win Gift vouchers upto Rs 500/-

View courses by askIITians

Design classes One-on-One in your own way with Top IITians/Medical Professionals

Click Here Know More

Complete Self Study Package designed by Industry Leading Experts

Click Here Know More

Live 1-1 coding classes to unleash the Creator in your Child

Click Here Know More

a Complete All-in-One Study package Fully Loaded inside a Tablet!

Click Here Know More